The present invention relates to an energy saving image-forming apparatus, and more particularly to an energy saving image-forming apparatus and a control method therefor which turns off power to circuits within the apparatus responsible for heavy power consumption when the image-forming apparatus is not used for a predetermined period of time.
The advent of the modem office has produced a marked increase in the use of equipment such as computers, facsimiles and duplicators. With many of these items, the amount of time the equipment is actually used is only twenty to thirty percent of total operating time. Accordingly, power consumed during periods of non-use (i.e. seventy to eighty percent of total operating time) is wasted unnecessarily. In an effort to promote environmentally safe products, the EPA (Environmental Protection Agency) has instituted a "green" designation for various types of equipment. For instance, when a computer with the "green" designation is not used for a predetermined period of time, the computer turns off power to components, such as the monitor, responsible for heavy power consumption. Accordingly, power is conserved while a user's exposure to potentially harmful electromagnetic waves is minimized. During this period of non-use, some components such as the ventilating fan are turned off, thereby reducing noise. Programs such as the "green" designation are adopted as part of EPA regulations.
Pursuant to the general industry trend of producing energy saving office equipment, several efforts have been made to make such equipment more and more power efficient. One effort is disclosed in U.S. Pat. No. 4,642,448 entitled Electrostatic Copying Apparatus issued to Shigemura et al. on 10 Feb. 1987. In this effort, an image forming apparatus is provided with an electrical heater having a heat controller for controlling energization and deenergization of the heater on the basis of detected temperature. The device also includes a manually operable power saving switch that produces a power saving signal to which the heat controller is partially responsive. Although that controller may produce some energy savings, I have found that a greater level of power efficiency can be obtained through the use of other techniques.
A more recent effort is disclosed in U.S. Pat. No. 5,241,349 entitled Image Forming Apparatus Having A Plurality Of Control Modes Of Thermal Fixing Apparatus issued to Nagasaka on 31 Aug. 1993. Here again, an image forming device is equipped with a section for controlling the temperature of a thermal fixing unit within the device. The device features three temperature control modes, each mode providing an additional level of energy savings. Although Nagasaka's effort reduces power being supplied to the thermal fixing unit in situations of reduced use, the embodiment described still provides no mechanism to reduce power to other portions of the device that are separately responsible for consuming large amounts of energy. Moreover, I have found that the energy efficiency of this device can be improved upon.